is there a danger of the family getting embroiled in a money laundering investigation

1. It is perfectly OK to deal in cash, so long as it is legitimate.

2. Unfortunately, the fact is it is possible "questions will be asked".† It is extremely unlikely, but, possible.

3. IF "questions are asked" you are totally, completely, absolutely, 100% in the clear and normal and will face no problems. You will just state "Grandpa hoarded cash."

You will NOT be "embroiled in a money laundering investigation". You MAY get asked one simple question, with no consequences or problems arising.

It's an unfortunate reality of the modern world that in most jurisdictions, the fact is you can occasionally "get asked about" cash transactions. (Whether by the bank due to KYC, the relevant authorities, or the bank at the behest of the authorities.)

This is absolutely unavoidable, unfortunately.

It's just like, say, you will occasionally be random tested for drunk driving.

In your situation you MUST take the cash to deposit it, so, it is unavoidable - you should proceed.

It is completely normal that (unfortunately) you may be queried on it, but, it's totally and completely OK - like being randomly tested for drunk driving.

† For example, in France once, the bank (at the behest of the relevant authorities) "pulled me up" and asked why the hell I was withdrawing so much cash. The reason was legitimate and simple, to buy antiques, so - no issue.

is there a danger of the family getting embroiled in a money laundering investigation

1. It is perfectly OK to deal in cash, so long as it is legitimate.

2. Unfortunately, the fact is it is possible "questions will be asked".† It is unlikely, but, possible. This is in the UK, 2020, with the specific amount discussed.

3. IF "questions are asked" you are totally, completely, absolutely, 100% in the clear and normal and will face no problems. You will just state "Grandpa hoarded cash."

You will NOT be "embroiled in a money laundering investigation". You MAY get asked one simple question, with no consequences or problems arising.

It's an unfortunate reality of the modern world that in most jurisdictions, the fact is you can occasionally "get asked about" cash transactions. (Whether by the bank due to KYC, the relevant authorities, or the bank at the behest of the authorities.)

This is absolutely unavoidable, unfortunately.

It's just like, say, you will occasionally be random tested for drunk driving.

In your situation you MUST take the cash to deposit it, so, it is unavoidable - you should proceed.

It is completely normal that (unfortunately) you may be queried on it, but, it's totally and completely OK - like being randomly tested for drunk driving.

† For example, in France once, the bank (at the behest of the relevant authorities) "pulled me up" and asked why the hell I was withdrawing so much cash. The reason was legitimate and simple, to buy antiques, so - no issue.